Experimental validation of igneous rocks as filler material for packed bed system dedicated to small CSP plants 1MWel

Abstract

This study is based on an experimental evaluation of four igneous rocks as storage materials for a packed bed system. This system will be in conjunction with a 1 Mel Concentrated Solar Power (CSP) plant employing an Organic Rankine Cycle (ORC). The target temperature of the application ranges from 180 °C to 300 °C, which will be achieved through a Linear Fresnel solar field. In this endeavor, this work aims to identify the potential of locally collected rocks: dolerite, leucogabbro, wehrlite, and troctolite, for application in this medium-temperature thermal energy storage (TES) system. To assess their suitability, a prior short-term thermal stability tests were performed by applying five cycles using thermogravimetric and dilatometry techniques. Afterward, a durability test was conducted by subjecting the rocks to 380 cycles within a temperature range of 100 °C to 300 °C, under an air atmosphere. At the end of the test, an evaluation was assessed to analyze the evolution of mineralogical and structural stability. Furthermore, this study examined the development of critical thermophysical and mechanical properties for sensible storage materials. We concluded that, the hydrothermal alterations occurred in mafic rocks leucogabbro and dolerite, enhancing their thermomechanical properties. In contrast, ultra-mafic rocks, wehrlite and, troctolite maintained a stable mineralogical composition and structure, preserving their main properties after the durability test. Dolerite, wehrlite and troctolite are considered suitable for an air-packed bed system. For our target application, wehrlite presents the most potential rock as it combines high thermophysical and mechanical properties, along with stable petrographic characteristics.